Content addressable memory (CAM) is a type of computer memory used in certain high-speed searching applications. In CAM, input search data is compared against a table of stored data, and an address of the matching data is returned.
Binary CAM uses data search words consisting entirely of 1 s and 0 s. Ternary CAM (TCAM), on the other hand, allows a third matching state of “X” for one or more bits in the stored data, thus adding flexibility to the search. For example, a TCAM might have a stored word of “10XX0” which will match any of the four search words “10000”, “10010”, “10100”, or “10110.”
Relatively large current and power supply voltage variations are required in a TCAM as the TCAM begins and ends search operations. For example, transitions from a low current demand operation, e.g., a non-search operation, such as a READ operation, WRITE operation, or a no-operation (NOOP) to a high current demand operation, e.g., a search operation, cause relatively large current and power supply voltage variations. These variations can cause functional, timing, and/or other problems within the TCAM and in surrounding components, e.g., other logic/core components on an integrated circuit in which the TCAM is implemented.
To reduce current and power supply voltage variations, Deep Trench (DT) capacitors may be used. However, a DT capacitor is not widely available in environments in which TCAM may be built. Other structures, such as n-well capacitors (NCAPs) or metal-insulator-metal (MIM) capacitors can be used, but provide much less capacitance per unit area.